Forging machine and method



K. SCHEUCHER FORGING MACHINE AND METHOD Feb. 27, 1968 4 Sheets-Sheet 1 Filed Oct 21, 1965 INVENTOR. K424 SCHfK/CHKQ ATTORNEYS "1") $41. EAL

Feb. 27, 1968 sc uc 3,370,450

FORGING MACHINE AND METHOD Filed Oct. 21, 1965 4 Sheets-Sheet 2 I1\"VE1\"TOR. 6 04506522 m W an-#rWA'PTORNERS Feb. 27, 1968 K. SCHEUCHER 3,370,450

FORGING MACHINE AND METHOD Filed Oct. 21, 1965 4 Sheets-Sheet 3 Fig-'3 IN VENTOR. K424 @aA iaoexe F i i w M A W z r United States Patent 3,370,450 FORGING MACHINE AND METHOD Karl Scheucher, Waite Hill, Ohio, assignor to TRW Inc.,

Cleveland, Ohio, a corporation of Ohio Filed Oct. 21, 1965, Ser. No. 499,952 18 Claims. (Cl. 72-354) ABSTRACT OF THE DISCLOSURE This invention relates to a die forging machine with a secondary closure mechanism sealing ofl? the die cavity which maintains a desired controlled external load on the forging dies developed from movement of the press ram. This load may remain constant even though internal die pressure increases or may be correlated with internal die pressure to balance internal and external die pressures or loads or lessen the ditferences between these pressures or loads. Specifically, the invention deals with a secondary die closure mechanism for incorporation in mechanical forging presses to control the external load on the forging dies relative to the internal die load created by the work piece as it is deformed by the ram of the press, thereby making possible the use of fragile dies in high pressure forging apparatus. The invention also includes the method of controlling external pressures on forging dies and specifically, in relation to pressure developed within the dies, thereby reducing die stresses.

The invention will be hereinafter specifically described as a secondary die closure mechanism for high pressure mechanical presses, which controls the external load on the dies of the press relative to the internal die pressure developed by the press so that the dies are not subjected to high pressure load differentials. This increases die life, maintains accurate die dimensions and makes possible the use of fragile dies. The secondary closure mechanism of this invention will be specifically described in connection with apparatus for the radial forging of gears. It will of course, be understood that other environments and other embodiments of the invention may vary widely from the specifically illustrated and hereinafter described embodiment, and, therefore, the scope of the patent is not limited to the specifically disclosed embodiments.

The secondary closure mechanism of this invention has a closed hydraulic system that uses pressure obtained from movement of the press ram and the activating hydraulic pressure can be controlled to provide a constant pressure on the die as the ram continues its movement,

or can provide an increasing pressure on the die for balancing the internal die pressure. Since the full load of the ram is not imparted to the die, and since the die closing load can be any selected portion of the ram load on the workpiece, die stresses are controlled to greatly increase the die life and to make possible use of exotic die material which could not withstand full ram pressures. The movement of the press ram on its pressure stroke causes movement of the secondary closure mechanism of this invention in advance of the ram until the closure mechanism engages the forging die. As the ram continues its pressure stroke, the pressure created on the die is controlled by metering hydraulic fluid through ori- 3,370,450 Patented Feb. 27, 1968 fices which are successively opened as the ram stroke continues. These orifices may be so sized and so positioned as to maintain a constant closing load on the die or they may be so sized and so positioned as to build up the closure pressure on the die in accordance with the internal pressure developed inside of the die by the workpiece. In radial forging of toothed members such as gears, turbine wheels and the like, the dies may have the tooth forming portions composed of inserts not capable of withstanding full ram loads and yet highly desirable for properly shaping and finishing the forgings. This invention makes use of such low strength inserts.

The secondary closure mechanism of this invention confines the workpiece to the die cavity and eliminates flash and other irregularities generated with the use of open dies.

It is, then, an object of this invention to provide a secondary closure apparatus for forging presses, which derives a closing pressure force from the press load but which proportions this force as desired.

Another object of this invention is to provide a secondary closure mechanism for mechanical presses, which controls the load on the forging dies while completely closing the die cavity.

Another object of this invention is to provide a closure mechanism for mechanical die presses, which has a closed hydraulic system actuated by movement of the press ram and creating closure pressures as desired on the forging dies.

Another object of the invention is to provide an impact forging apparatus with a secondary closure mechanism which will build up a closing load in proportion to the internal pressure developed in the dies by the workiece. p Another object of the invention is to provide a method of radial forging under controlled die loads energized by loads on the workpiece.

Another object of this invention is to provide a method of radially forging gears where external loads on the forging dies are correlated with internal loads developed in the dies.

A still further object of this invention is to provide a method of radially forging gears and the like toothed articles where radial metal flow is confined to a closed die cavity having a closing load proportioned relative to the internal load in the dies.

Other and further objects of this invention will be apparent to those skilled in this art from the following detailed description of the annexed sheets of drawings whlch, by Way of an example, illustrate a preferred embodiment of the invention.

On the drawings:

FIGURE 1 is an isometric view of a secondary closure apparatus, according to this invention, for mounting in a mechanical forge press;

FIGURE 2 is a transverse front-to-rear cross-sectional view of FIGURE 1 and showing the closure in partially opened position;

FIGURE 3 is a view similar to FIGURE 2, but showing the closure in closed position;

FIGURE 4 is a fragmentary isometric view, with parts broken away and shown in vertical cross-section, of the secondary closure and die assembly of the apparatus of FIGURES 1-3, showing the manner in which the same act on the work piece to form a radial gear;

FIGURE 5 is a vertical cross-sectional view, with parts in elevation, of the die and closure assembly of FIGURE 4, showing the same in closed position and illustrating a die forged gear shaped by the assembly and filling the die cavity;

FIGURE 6 is a view similar to FIGURE 5, but showing the assembly in open position and the initial blank or work piece from which the gear is formed;

FIGURE 7 is a vertical cross-sectional view taken through one of the metering pins of the apparatus of this invention, generally along the line VIIVII of FIG- URE 2;

FIGURE 8 is a transverse sectional view through the pin of FIGURE 7 along the line VIII-VIHof FIGURE 7; and

FIGURE 9 is a plan view of a finished radial gear made by the apparatus of this invention, and having a portion broken away for illustrating the grain flow lines of the metal produced by the apparatus of this invention.

As shown on the drawings:

In FIGURE 1, the reference numeral 10 represents generally the secondary closure apparatus of this invention for insertion in a high pressure mechanical forging press having a fixed bottom bed and a vertically moveable pressure applying head. The apparatus 10 is composed generally of a fixed bed 11 for mounting on the bed of the press, a top vertically moveable ram 12, and a plurality of guide pins or posts 13 arranged in rows along the sides of the bed 11 to slidably guide the ram 12, the ram having recesses slidably receiving the posts. The ram 12 carries a pair of pressurized tanks 14 for hydraulic fluid such as oil.

As shown in FIGURES 2 and 3, the bed 11 has a well v 15 in which is mounted the forging dies and ejection mechanism. As shown, a base plate 16 is bolted to the bottom of the Well and a mounting ring 17 is bolted to the base plate 16. A bottom adapter ring 18 is mounted in the aperture of the ring 17 and has a base flange 19 clamped between the ring 17 and the base plate 16. This adapter 18, in turn, carries a central die post 20 with an external bottom flange 21 clamped between the ring 18 and the base 16. The post 20 has a central aperture 22 therethrough receiving an ejection pin 23 which is actuated by a rod 24 slidably extended through the base 16 and through a suitable bearing mounting 25 in the main bed 11.

A top insert adapter ring 26 overlies the ring 18 in the mounting ring 17 and projects slightly above the top surface of the mounting ring. This adapter ring 26 has a counterbore 27 around the mouth thereof with a radial bottom shoulder and a tooth forming ring 28 is seated in this counterbore.

As shown in FIGURE 4, the tooth formingv ring 28 can be composed of a plurality of individual tooth segments 29 in side-by-side circumferential relation.

The secondary closure mechanism of this invention includes a closure ring 30 with a reduced diameter pilot portion 31 for bottoming on the adapter 26 in overlying relation to the die ring 28. The closure ring 30 has a cylindrical bore 32 therethrough receiving a punch 33 coacting with. the die post 20 to provide the top and bottom for the die cavity. The closure ring 30 is supported on the bottom of a closure adapter head 34, which head, in turn, is carried by an, annular closure slide or ring 35 slidably mounted in an annular cavity 36 of the ram 12. Suitable annular packing sleeves 37 line the cavity 36 to provide smooth walls slidably supporting the upper end of the slide ring 35 in sealing engagement therewith. The lower portion of the slide ring 35 is reduced in radial thickness only on the outer periphery thereof to provide a downwardly facing radial shoulder 38. The reduced thickness portion of the slide extending from this shoulder is sealingly engaged by packing rings 40 clamped between the sleeves 37 and loading rings 41 which are bolted to the underface of the ram head 12. An annular chamber 42 is thereby provided under the shoulder 38 and is adapted to receive hydraulic fluid from an inlet 42a,in the ram head for raising the slide 35 to the top of the chamber 36.

A ram head 43 extends from the arm 12 through the central aperture 44 of the slide 35 and carries a punch holder 45 which, in turn, carries the punch 33. It will, of course, be understood that the holder and punch are re- 4 spectively bolted to the bottoms of the ram head and punch holder.

The closure head 34 has lateraly extending arms 46 on which are supported metering pins 47 which are slidably mounted in open-bottom, closed-top cylinders 48 provided in the ram 12. These cylinders communicate with passages 49 joining the pressurized tanks 14 with the chamber 36 above the slide 35. The passages 49 have annular grooves 50 surrounding the cylinders 48 to provide windows around the pins 47. Each pin 47 has orifices 51 spaced along the length thereof to selectively communicate with the groove 50 and passage 49 as they pass the window provided by the groove. As shown in FIGURES 7 and 8, some of the orifices 51 are wide and some are narrow with a bottom orifice having widened mouths 52 at the opposite ends thereof. The positions and shapes of the orifices 51 are designed to produce a desired bleeding of hydraulic fluid from the chamber 36 as the ram descends so as to control the load or pressure which the closure ring pilot 31 exerts on the dies.

A pair of metering pins 47 and tanks 14 is provided for a fast flow of fluid along a shortened path. The pins are diametrically opposed and coact to quickly handle the desired bleed rate.

When the assembly 10 is in the partially open position 7 of FIGURE 2, fluid under pressure is admitted to the annular chamber 42 under the slide shoulder 38 and fluid is relieved from the top of the cavity 36 so that the secondary closure ring 30 can be held in a raised position. Then, as the ram 12 descends, the pilot 31 will come to rest on the insert adapter 26 and on the die ring 28 carried therein. Hydraulic fluid in the cavity 36 will be trapped as determined by the orifices 51 of the pins, and as the ram continues to descend, the load exerted on the slide 35 by this trapped fluid will be controlled to thereby control the load on the closure ring 30. At the same time, the descending ram 12 moves the punch 33 through the closure ring 30 to act on a cylindrical blank B in.

the die cavity. This blank B is supported on the die post 20 and the top of this die post as well as the bottom of the punch have identical annular beads 53 effective to enter the blank B and force metal therefrom radially outward into the teeth cavities provided by the die ring 28. As the punch 33 continues to descend and approach the die post 20, the blank B is flattened and radially expanded as will be more fully described in connection with FIG- URES 5 and 6. This action, of course, increases the internal pressure or load on the dies and the pin orifices 51 may be so designed as to balance this internal load with an external load on the dies, or to correlate the load relationship in any manner desired. As a result, the dies can be composed of very fragile materials which produce excellent finishes for the gears of this invention.

It will be understood that the descending ram 12 in sliding the cylinders 48 over the pins 47 will bring about a controlled bleeding of the hydraulic fluid in the cavity 36 back to the tanks 14 to, thereby, develop the desired load on the closure 30. The hydraulic circuit between the tanks and cavity 36 can be entirely closed, with the tanks maintaining a back pressure on the fluid so that when the ram is raised and the cavity 36 is expanded, the fluid can flow back into this cavity. It will, of course, be understood that fluid under pressure is admitted into the annular chamber 42 at the bottom of the slide to support the slide in the cavity. The admission of this fluid can be controlled through a suitable valve and pump or pressurized tank (not shown) arrangement. The function of the fluid in the annular chamber 42 is to raise the closure ring assembly with the ram when the ram is raised so that the dies will be opened for ejection of the finished gear G formed in the dies.

As best illustrated in FIGURES 5 and 6, the blank B initially rests on the bead 53 of the die post 20 and has an external diameter fitting freely in the aperture of the closure ring 30. The punch 33 fits snugly in the aperture of this closure 30 and its annular bead 53 addresses the top of the blank B. The blank B is essentially a cylindrical solid disk with flat top and bottom walls. The die ring 28, fitted in the counterbore 27 of the adapter die 26, is composed of a ring of tooth-forming members with an internal diameter slightly greater than the external diameter of the blank B so that a gap exists between the die ring and the periphery of the blank.

As the punch 33 is forced downwardly, the blank B is pierced by the beads 53 of the die post and the punch, and is squeezed into conformity therewith at the same time being radially expanded into the die ring 28 to form radial gear teeth T around the blank.

As shown in FIGURE 5, the finished gear G has a cenrtal hub portion H, a circular rim R joined with the hub through a reduced thickness web W and surrounded by a reduced thickness annular tooth face rim R from which the gear teeth T radiate. It will be noted that the closure 30 cooperates with the adapter ring 26, the punch 33 and the bottom die 20 to form a completely closed die cavity, shaping the finished gear G with the reduced thickness rim portion R formed by the opposed corners of the closure ring 30 and the counterbore 27 and with the tooth ring 28 forming the teeth T beyond this rim. The hub H is bottomed on the ejection pin 23 through the post 20. It will be especially noted that the completely closed die cavity from the open position of FIG- URE 6 to the closed position of FIGURE 5 effects movement of metal from the blank B into the finished gear shape G both axially and radially with most of the metal being moved by the beads 53 of the punch and bottom die post to form the reduced thickness web between the hub H and rim R.

The finished gear G as shown in FIGURE 9 thus has a central hub H, a circular rim R spaced concentrically from the hub and connected therewith by a reduced thick ness web W and, in turn, surrounded by a reduced thickness rim portion R forming the base of the radial gear teeth T. The broken-away portion of the gear G in FIG- URE 9 shows the grain flow lines of the metal created by the impact forging of the blank B in the closed die cavity. These flow lines include generally radially spaced circular lines 54 in the rim area R surrounded by wavy flow lines 55 in the rim area R and, in turn, surrounded by outwardly bowed flow lines 56 defining the gear teeth T. The sides and bases of the teeth T are, therefore, defined by the sides only of the grain flow lines to provide maximum strength and wear resisting surfaces.

The impact forging of the blank B occurs in a single stroke to form the finished gear G and creates plastic deformation of the blank metal into the completely closed die cavity. During this impact forging, the metal grains of the blank metal align themselves with their longest dimension parallel to the direction in which the metal is flowing, creating flow lines along the boundaries of the grains. The illustrated flow lines 54, 55 and 56 are so oriented and related as to produce the strongest possible grain configuration for resisting stresses which the gear encounters in operation. Thus, the rim R, by being composed of succeeding circular flow lines 54, has the strength for resisting radial expansion and contraction. Then, as these flow lines are expanded first through the wavy portions 55 in the rim area R and then to the more inclined bowed portions 56 in the teeth T, radial torque resisting strength is imparted to the teeth. Of course, since all exposed areas of the teeth are defined only by the sides of these flow lines, there is no exposed ends of flow lines and a superior wearing tooth surface is provided.

Since, as explained above, the external pressures on the dies are controlled and can be related to the internal pressures developed within the dies, the tooth ring 28 to form the teeth T can be composed of die materials which will create finished surfaces on the teeth even though these materials do not have a very high strength. In fact, ceramic 6 inserts 29, as illustrated in FIGURE 4, can be used to form the tooth ring. The tooth ring is completely surrounded and covered by the adapter 26 and the closure 30, and its shape and dimensions will be maintained by these surrounding and covering members.

Because the die forging cavity is completely closed, a finished gear, free from flash, can be produced by a single stroke of the press. The weight of the blank B is carefully controlled to provide the exact amount of material for filling the die cavity at the end of the punch stroke without creating flash. It is preferred that the diameter of the blank B be as large as possible. The length-to-diameter ratio of the blank is therefore carefully controlled so that the diameter will approximate the root diameter of the gear teeth.

The blank B is bar stock, preferably composed of a carbun'zing grade of steel such as A181 9310. The blank is turned and polished to a previously determined proper weight for providing just enough metal to form the completed gear. It is then heated in an inert atmosphere or induction furnace to temperatures of about 1800 F. The impact forging is carried out at this temperature. When the press is opened up, the ejection rod 24 is raised to cause the pin 23 to knock the finished gear out of the die cavity. The gear is then air cooled to room temperature, next heated to temperatures of around 1550 F. for about one hour in an inert atmosphere and then oil quenched. Next, the quenched gear is tempered at about 1100 F. for two hours and then air cooled.

The surfaces of the die cavity are preferably coated with a graphite lubricant to prevent sticking and to insure a good finish for the gear.

It should be understood that the apparatus and method of this invention include the sealing of the die cavity with a closure member and the maintenance of a sealing load by a built-in self-bleeding hydraulic control which can be correlated with punch loads on the work piece in the cavity as desired. In some operations, it is desirable to close the die cavity with a fixed load or pressure from the secondary closure assembly and in other operations, it is desirable to increase the load or pressure of the secondary closure assembly on the dies as the punch load or pressure on the work piece increases. Various load differentials or balances can, thereby, be created and maintained between the internal die loads and pressures and the external die loads and pressures. Since the hydraulic system for creating these differentials is self-actuating and built into the apparatus, special attention of an operator is not needed and the operation is entirely automatic, foolproof, and immediately effective.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent granted hereon, all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. In a forge press having a forgingdie, a punch coacting with said die, and a ram actuating said punch, the improvement of a secondary die closure which includes means movably carried by said ram for covering the die cavity formed by the die and punch, and a closed hydraulic circuit hydrualically controlled by relative movement between the ram and closure for selectively regulating the load on the closure.

2. In a forging machine including an impact punch and a forging die for shaping a workpiece impacted by said unch, the improvement of a secondary die closure moveably mounted around the punch and sealing the die cavity in which the work piece is seated, and a closed hydraulic circuit selectively controlling the load on said secondary closure and actuated by relative movement between the closure and punch to vary the external pressure on the die cavity to increase said external pressure as the internal pressure created by movement of the punch is increased.

3. In a forging machine having a fixed forging die and a movable punch coacting with said die to die forge a workpiece into conformity with the die and punch, the improvement of a secondary closure for said die having means bottomed on the die and receiving the punch therethrough hydraulic means for pressing said closure on said die, metering means for said hydraulic means controlling hydraulic load on the closure, and means for raising the closure from the die, said metering means selectively actuated by movement of the punch.

4. In a forging press, a bed, a ram movable toward and away from said bed, a forging die mounted in said bed, a punch mounted on said ram coacting with said die to form a die shaping cavity, a closure ring surrounding said punch and coacting with said die for sealing the die cavity formed by the die and punch, means slidably supporting said closure ring in said ram, means for flowing hydraulic fluid between the ram and means for supporting the closure ring for forcing the ring against the die, and orifice means moveable with said closure ring controlled the flow of hydraulic fluid for determining the load on the closure ring in relation to the position of the ram.

5. A forging machine which comprises a bed, a ram moveable toward and away from said bed, a forging die mounted on said bed, a punch coacting with said die mounted on said ram, a closure ring surrounding the punch adapted to be bottomed on the die for sealing the die cavity, piston means slidably supporting said closure means on said ram, means for introducing fluid under pressure between the ram and piston means for controlling the load on the closure means, and means moveable with said closure slidable in said ram for controlling hydraulic flow to said piston means, whereby the load on said closure means is controlled relative to the position of the ram.

6. A forging machine which comprises a bed, a ram moveable toward and away from said bed, a die carried by said bed, a punch carried by said ram coacting with said die, a closure ring surrounding said punch and coacting therewith for sealing the die cavity, an annular support for said closure ring slidably mounted in said ram, means for introducing fluid between the ram and support when the ram is in spaced relation from the bed to bottom the closure ring on the die, means bleeding fluid out of the ram as the ram is moved toward the bed for relieving load on the closure ring, and said means for relieving fluid being slidable in the ram with the support for the closure means.

7. In a forging machine having a bed, a ram moveable toward and away from the bed, a die assembly mounted in the bed, a punch mounted on the ram for coacting with the die assembly to provide a die cavity and ejector mechanism for removing a forged article from the cavity, the improvement of a closure ring slidably mounted on the ram surrounding the punch and adapted to be bottomed on the dies for sealing the die cavity, means for introducing fluid between the ram and mounting for the closure ring to force the closure ring against the die, means trapping fluid between the mounting for the closure ring and the ram to load the closure ring as the ram moves toward the bed, and orifice pins moveable with the closure ring for bleeding fluid trapped between the support for the closure ring and the ram to control the load on the closure ring as the ram moves toward the bed.

8. A forging machine which comprises a ram, a punch fixedly carried by said ram, an annular slide surrounding the punch and slidably mounted in the ram, said ram having an annular fluid chamber above the slide ring, tank means for supplying hydraulic fluid to said chamber, an orifice pin moveable with the slide ring controlling the bleeding of hydraulic fluid from the annular chamber as the ram advances on a pressure stroke, and a closure ring surrounding the punch for sealing a die cavity receiving the punch.

9. A forging machine which comprises a ram having a central punch head, an annular chamber in said ram surrounding said punch head, an annular slide mounted in said chamber, means for introducing fluid under pressure into the annular chamber above the slide, a metering pin moveable with the slide controlling bleeding of hydraulic fluid from said annular chamber, means for lifting the slide into the annular chamber, a punch carried by said punch head, and a closure ring carried by said slide surrounding said punch to coact therewith for closing a die cavity.

10. A forging machine which comprises a bed, a die assembly mounted on said bed, a ram moveable toward and away from said bed, a punch head carried by said ram, a punch supported on said head, an annular chamber in said ram surrounding said punch head, an annular slide mounted in said annular chamber, a closure ring surrounding said punch carried by said slide, cylinders in said ram, pins slidably mounted in said cylinders,'tank means supplying oil to said pins, orifices in said pins along the length thereof for controlling bleeding of oil from the annular chamber above the slide to the tank means as the ram descends toward the bed, a closure ring carried by the slide surrounding the punch for coacting therewith to seal the die cavity, and the orifices in said pins controlling the load on said closure ring as the ram advances toward the bed.

11. A forging machine which comprises a ram having a fluid cavity, a slide in said cavity and depending therefrom below the ram, a die closure ring supported by said slide below said ram, said slide having a reduced diameter lower portion coacting with the surrounding cavity wall to provide an annular chamber separated from the main' cavity by the slide, means for introducing fluid under pressure into said annular chamber for lifting the slide toward the top of the cavity, and means carried by the closure ring for controlling bleeding of hydraulic fluid from the cavity above the slide as the ram advances on its pressure stroke to thereby control the load on the closure ring.

12. In a forging machine having a die, a punch coacting with said die, and a secondary closure moveable relative to the punch and die sealing the die cavity provided by the punch and die, the improvement of means for loading said secondary closure in proportion to internal pressures developed in the die cavity by the punch for decreasing pressure diflerentials between the inside and outside of the dies said means selectively controlled by movement of the punch.

13. A gear forging machine which comprises a bed, a die mounted in said bed having a tooth forming ring, a die closure ring overlying the tooth forming ring, a punch moveable through the die closure ring for forging a blank into the tooth ring to provide gear teeth around the blank, and means controlling the load on the die closure ring relative to the internal load in the tooth ring for relieving stresses on the tooth ring said means selectively controlled by movement of the punch.

14. The method of forging which comprises inserting a heated blank into a die cavity, pressing a punch against the blank, pressing a seal ring against the die around the punch, and selectively relieving load on the seal ring as the punch advances into the die cavity for controlling external die load relative to internal load.

15. The method of die forging which comprises advancing a punch through a die closure ring, loading the ring with fluid under pressure developed by the advancing punch, and selectively bleeding the fluid to relieve the load on the closure.

16. The method of die forging which comprises bottoming a closure member on a die, advancing a punch through the closure member to act on a workpiece in the die cavity closed by the closure member, loading the closure with oil under pressure as the punch advances into the die cavity, and selectively bleeding oil to relieve load on the closure as the punch advances.

17. The method of die forging which comprises trapping oil between a ram and a mounting for a closure ring carried by the ram, and selectively bleeding trapped oil as the ram advances on its pressure stroke for controlling the load on the closure.

18. The method of die forging radial gears which comprises supporting a cylindrical metal blank on a raised annular bead in a die cavity, surrounding the blank With a tooth ring, bottoming a closure ring over the tooth ring, forcing the annular bead of a punch against the blank within the closure ring, advancing the punch into the die cavity to force the metal on opposite sides of the blank 19 ring, and selectively controlling the closure load of the closure ring on the tooth ring relative to the advancement of the punch in relation to the internal load on the tooth ring for relieving stresses therefrom.

References (Zited UNITED STATES PATENTS 1,569,135 11/1925 Bell 72354 2,261,304 ll/1941 Sparks 72-353 10 3,964,450 11/1962 Strugala ct al. 72-654 FOREIGN PATENTS 5,537 3/1892 Great Britain.

into conformity with the die cavity and into the tooth 5 CHARLES LANHAM, Primary Examiner 

